1. Field of the Invention
This invention relates generally to percussive tools having a removable work bit, and more specifically, this invention relates to a tamping tool for railroad bed tamping apparatus having an easily removable and replaceable tamping foot.
2. Description of the Prior Art
Percussion tools have a work bit or work area that bears the brunt of the percussive impact. Accordingly, it is desirable to have this work bit formed of a material that is as hard as possible, as the impact forces tend to cause the work bit to become worn and to fail in a relatively short time. Also, in some percussive tools it is desirable to be able to achieve different functions, which requires different work bits. Therefore, it is desirable to be able to change the work bits to provide these different functions, as well as to replace work bits as they become worn out.
Tamping tools for use with railroad bed tamping equipment illustrate a particular type of percussive tool in which these problems are encountered. Gross movements and primary tamping action of the tamping tools is achieved by a suitable drive mechanism, such as a pneumatic or hydraulic system. In addition, the tamping tools are given a vibratory motion at a relatively high frequency, usually by means of an electrical drive arrangement.
In the most common form of prior art tamping tool, the shank and tamping foot of the tool are unitarily formed. As it is desirable to have a relatively soft workable material for the shank, while the tamping foot should be as hard as possible to resist wear produced by the tamping action, a compromise is necessary. Accordingly, the tamping foot is generally of a softer metal than preferable, which means that the tamping tool has to be replaced relatively frequently. As the shank and tamping foot are integrally formed, this means that the entire tamping tool must be replaced. This is, of course, a relatively expensive proposition, and the handling of the relatively large tamping tool creates additional problems. Accordingly, it would be most desirable if a tamping foot formed of a hard material could be selectively removed for replacement by a new tamping foot, upon the original tamping foot becoming worn. In addition, such a removable tamping foot would permit the substitution of different foot configurations upon encountering different ballast materials or conditions, as well as the substitution of other types of tools or work bits.
Various attempts have been made to provide removable tamping feet. The most common approach of this sort is the utilization of threaded bolts or screws, or transversely extending pins. One of the difficulties with these approaches is that it is necessary for the operator to carry appropriate tools to effect the change in a tamping foot. Another very significant difficulty is that the ballast with which the tamping foot is being utilized tends to work around the bolts or pins to produce a sealing action, which greatly hampers removal of the tamping foot.
Another approach has been to affix the tamping foot by a force fit, sometimes with the addition of an adhesive. Removal of the tamping foot is then achieved by striking the foot with a suitable instrument. As the tamping foot must be driven on the shank with considerable force in order to prevent its becoming unattached during tamping, the force of the blows to achieve desired separation must be relatively large. Thus, not only is considerable effort required to remove the tamping foot, but there is also considerable risk of damaging the relatively soft shank.